Sustained Effect of Hyaluronic Acid in Subcutaneous Administration to the Cochlear Spiral Ganglion

Protective effect of astaxanthin nanoemulsion on mammalian inner ear hair cells

Background

Aminoglycoside antibiotics are used for treating certain acute infections. However, these drugs cause ototoxicity by inducing inner ear hair cell death.

Aims/Objectives

We investigated the protective effect of a nanoemulsion of the carotenoid astaxanthin on mammalian inner ear hair cells against neomycin-induced ototoxicity.

Material and Methods

Dose-response relationship, quantification of hair cell loss, and reactive oxygen species production were assayed in response to neomycin with and without astaxanthin in cultured utricles of CBA/N mice. In addition, auditory brain response (ABR) and hair cell loss after exposure to the nanoformulation and loud noise were examined in vivo in guinea pigs.

Results

Astaxanthin suppressed neomycin-induced reduction of hair cells by reducing the production of hydroxy radicals. Furthermore, hair cell loss in the second rotation of the cochlea was significantly lower in the astaxanthin group than in the noise-only group.

Conclusions and Significance

The blood-labyrinth barrier limits the successful delivery of drugs for inner ear complications. However, in the nanoemulsion form, astaxanthin can penetrate the round window (fenestra ovale) membrane, enabling topical administration. Thus, astaxanthin nanoemulsion could be useful in treating ototoxicity in individuals with inner ear complications.

In Vivo Imaging Analysis of an Inner Ear Drug Delivery in Mice: Comparison of Inner Ear Drug Concentrations Over Time

Treatment for inner ear regeneration and protection needs local injection of steroid or new drug for inner ear regeneration into the round window membrane (RWM) in cochlea, but a systemic injection is not available due to its systemic side effects. However, pharmacokinetics of therapeutic agents or steroid locally injected into the inner ear is not well known. Hence, we introduce a new method for the real-time observation of drug delivery in transgenic animals in vivo. We exemplify mice which contain a firefly luciferase (FLuc) gene expression cassette regulated by the murine glial fibrillary acidic protein (GFAP) promoter. Luciferin delivered into the inner ear of those mice reacts with FLuc that is expressed in the GFAP-expressing cells in the cochlear nerve and spiral ganglion, and the resulting bioluminescence is detected by a camera. Using this system, we show the imaging of pharmacokinetic differences between local and systemic (intravenous and subcutaneous) injections of the inner ear.

Comparison of Drug Availability in the Inner Ear After Oral, Transtympanic, and Combined Administration

Although combination of oral and transtympanic drug therapy (CT) has been proved more effective and safer for idiopathic sudden sensorineural hearing loss (ISSNHL) by some clinical trials, there are few laboratory researches on the pharmacokinetics in the inner ear following CT on account of structural limitations of the inner ear. The aim of the present study was to investigate the pharmacokinetic behaviors of CT in the inner ear of mice. Eighteen transgenic GFAP-Luc mice which express luciferase in cochlear spiral ganglion cells were divided into oral administration (OR) group, transtympanic injection route (TT) group and CT group, and luciferin was delivered into the inner ear of these mice through oral, transtympanic or combined routes, respectively. A new in vivo imaging system was used to observe luciferin/luciferase signals and the compare the pharmacokinetics of different administration routes in the inner ear of mice. Bioluminescence signals were observed in the inner ear 3.3 ± 2.6 min after CT, significantly earlier than that of OR group (15.8 ± 7.4 min). CT owned the longest reaching-peak time and largest area under the curve (AUC) among three groups. Compared to TT, CT had longer biological half-life and higher AUC value, but did not displayed stronger peak value. There were significant differences in the peak values between OR group and TT group and between OR group and CT group. This study suggests that the OR route is less effective than the TT or CT route, and combination of OR and TT can deliver more drugs into the inner ear and confer a longer therapeutic window, but cannot increase drug intensity.

Comparison of hearing outcomes in stapedotomy with fat and Hyaluronic acid gel as a sealing material: a prospective double-blind randomized clinical trial

PURPOSE

In the literature on stapes surgery, various materials have been used to seal the vestibulotomy. To date, there are only a few published randomized clinical trials with focus on hearing outcomes, using different sealing materials. Hence, the aim of this study was to compare hearing outcomes when using fat or Hyaluronic acid gel (HAG) to seal the stapedotomy.

METHODS

The present double-blind, prospective, randomized clinical trial was conducted on ears undergoing stapedotomy in Dasthgheib Hospital, a referral otology center in Southern Iran, and Dena private hospital, Shiraz Iran. A total of 150 primary stapedotomies were evaluated, and sealing material was fat in 77 ears and HAG in 73.

RESULTS

60 (77.9%) of the fat group ears and 63 (86.3%) of the HAG group ears obtained postoperative air-bone gap (ABG) within 20 dB, but the difference was not significant (p = 0.182).

CONCLUSION

As a sealing material in stapedotomy, HAG is comparable with fat in terms of hearing outcomes. Therefore, HAG is recommended as a safe sealing material in stapedotomy.

Comparison of inner ear drug availability of combined treatment with systemic or local drug injections alone

Combination of systemic and local drug therapy has been proved more effective and safer for idiopathic sudden sensorineural hearing loss by some clinical trials, and there are few laboratory researches on its pharmacokinetic behaviors in the inner ear. In the present study, we use a new in vivo imaging system to compare the pharmacokinetics of combined therapy (CT), with intravenous (IV) or transtympanic (TT) injection alone in both ears of transgenic GFAP-Luc mice. Biological half-life, total photon counts and the area under the curve (AUC) value significantly increased after CT. However, adding IV to TT injection cannot strengthen the peak photon of the drug in the inner ear. In addition, when D-luciferin is injected to the left ear the volume of total photon count and AUC value of CT-left ear are larger than the combined volume of TT-left ear and IV-left ear, suggesting a synergistic effect, and those of CT-right ear are almost equal to the summation of those of IV-right group and TT-right group, suggesting no amplifying effect on the risk of systemic side effect. This study showed that CT could deliver more drugs into the inner ear, and brought a longer therapeutic window, and were more effective than intravenous or transtympanic injection alone in the pharmacokinetics.